Cardioplegia at subnormothermia facilitates rapid functional resuscitation of hearts preserved in SOMAH for transplants

OBJECTIVES: Hearts preserved ex vivo at 4°C undergo time-dependent irreversible injury due to extreme hypothermia. Studies using novel organ preservative solution SOMAH, suggest that hearts are optimally `preserved' at subnormothermic temperature of 21°C. Present study evaluates relative efficacy of SOMAH `cardioplegia' at 4 and 21°C in preservation of optimum heart function after in vitro storage at subnormothermia. METHODS: Porcine hearts arrested with SOMAH cardioplegia at 4 or 21°C were stored in SOMAH for 5-hour at 21°C (n = 5). At the end of storage, the weight of hearts was recorded and biopsies taken for cardiac tissue high energy phosphate level measurements. The hearts were then attached to a reperfusion apparatus and biochemical parameters including cardiac enzyme release and myocardial oxygen consumption and lactate production were determined in perfusate samples at regular intervals during ex vivo perfusion experiment. Functional evaluation of the hearts intraoperatively and ex vivo was performed by 2D echocardiography using trans-esophageal echocardiography probe. RESULTS: Post-storage heart weights were unaltered in both groups, while available high-energy phosphates (HEP) were greater in the 21°C group. Upon ex vivo reperfusion, coronary flow was significantly greater (p < 0.05) in 21°C group. 2D echo revealed a greater cardiac output, fractional area change and ejection fraction in 21°C group that was not significantly different than the 4°C group. However, unlike 4°C hearts, 21°C hearts did not require inotropic intervention. Upon reperfusion, rate of cardiac enzyme release temporally resolved in 21°C group, but not in the 4°C group. 21°C working hearts maintained their energy state during the experimental duration but not the 4°C group; albeit, both groups demonstrated robust metabolism and function during this period. CONCLUSIONS: Rapid metabolic switch, increased synthesis of HEP, decreased injury and optimal function provides evidence that hearts arrested at 21°C remain viably and functionally superior to those arrested at 4°C when stored in SOMAH at ambient temperature pre-transplant. ULTRAMINI-ABSTRACT: Cardioplegic arrest and preservation of hearts in SOMAH at ambient temperature efficiently conserves metabolism and function in in vitro porcine model of heart transplant. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13019-014-0155-z) contains supplementary material, which is available to authorized users.